Power-rail adapters of the above-described type are the state of the art. They serve for the connection of a light fixture, in particular a spotlight fixture, with a power rail and at the same time provide for a mechanical fixation, that is, a fixation of the fixture on the building surface, in particular on the ceiling of a building and at the same time for the electric connection of the light fixture with conductors in the power rail. Light fixtures that can be connected to a power rail via a power-rail adapter are also well known and quite common. They have as well been fabricated by applicant for decades.
First, a light fixture that is not suitable for connection to a power rail by means of a power-rail adapter will be described for providing background information and a better understanding of the invention. As an example, reference is here made to a focal flood fixture that is described in the current catalogue of applicant in the 2004/2005 edition on page 486 and the following and that has several differently colored light sources. The light sources are connected to power-supply lines that provide line voltage or operating voltage for the light sources. Furthermore, the fixture has three electronic ballasts so that the three light sources can be controlled individually. The ballast can for example be a ballast functioning according to the DALI protocol that can be addressed individually and that is connected to a signal line. The light fixture can be integrated into a lighting system and can receive control information from a central controller via the signal line. For example, it is possible to transmit instructions from the central controller to one of the light sources of the light fixture to switch to a particular dimming state, e.g. for the purpose of mixing colors, to blink, to switch on, to switch off, or the like.
The power-supply line, which generally is associated with a phase conductor and a null conductor, is typically connected to the light fixture via a first conductor and transfers for example an operating voltage of 230 VAC or 110 VAC. For connection of the signal line, a second connection is provided on the light fixture or on the operating unit assigned to the light fixture, that is, e.g. the electronic ballast. The signal line typically is a two-conductor line that transfers voltages up to 25 V for example. The signal line is normally physically separate from the power-supply lines.
In a light fixture of this type that consequently disposes of a connection for a power-supply line and of a connection for a signal line for receiving control information, there exists a need to connect such a light fixture via a power-rail adapter to a power rail.